1. Field of the Invention
The present invention relates to an ultrasonic probe to be used when extracavitary scan or intracavitary scan is performed on an object to be inspected.
2. Description of a Related Art
In medical fields, various imaging technologies have been developed in order to observe the interior of an object to be inspected and to make diagnoses. Especially, ultrasonic imaging for acquiring interior information of the object by transmitting and receiving ultrasonic waves enables image observation in real time, and provides no exposure to radiation unlike other medical image technologies such as X-ray photography or RI (radio isotope) scintillation camera. Accordingly, ultrasonic imaging is utilized as an imaging technology at a high level of safety in a wide range of departments including not only the fetal diagnosis in the obstetrics, but gynecology, circulatory system, digestive system, etc.
The ultrasonic imaging is an image generation technology utilizing the nature of ultrasonic waves that the waves are reflected at a boundary between regions with different acoustic impedances (e.g., a boundary between structures). Typically, an ultrasonic imaging apparatus (or referred to as an ultrasonic diagnostic apparatus or an ultrasonic observation apparatus) is provided with an ultrasonic probe to be used in contact with the object or ultrasonic probe to be used by being inserted into a body cavity of the object. Alternatively, the ultrasonic imaging apparatus may be provided with an ultrasonic endoscope in combination of an endoscope for optically observing the interior of the object and an ultrasonic probe for intracavity. From such an ultrasonic probe or ultrasonic endoscope (hereinafter, refereed to as an ultrasonic probe or the like), ultrasonic beams are transmitted toward the object such as a human body and ultrasonic echoes generated in the object are received by using the ultrasonic probe or the like, and thereby, ultrasonic image information is acquired. On the basis of the ultrasonic image information, contours of structures (e.g., internal organs, diseased tissues, or the like) existing within the object are extracted by obtaining reflection points, where ultrasonic echoes have been generated, and reflection intensity.
In a general ultrasonic probe, an ultrasonic transducer for transmitting and receiving ultrasonic waves is configured of a vibrator (piezoelectric vibrator) having electrodes formed on both sides of a material that has a piezoelectric property (a piezoelectric material) such as a piezoelectric ceramics represented by PZT (Pb (lead) zirconate titanate), a polymeric piezoelectric material represented by PVDF (polyvinylidene difluoride), or the like. When a pulsed or continuous wave voltage is applied to the electrodes of the vibrator, the piezoelectric material expands and contracts. By the expansion and contraction, pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and an ultrasonic beam is formed by synthesizing these ultrasonic waves. Further, the respective vibrators expand and contract by receiving propagating ultrasonic waves to generate electric signals. These electric signals are outputted as detection signals of the ultrasonic waves. A plurality of such ultrasonic transducers are arranged and sequentially driven, and thereby, an ultrasonic beam is formed by synthesizing ultrasonic waves transmitted from the respective ultrasonic transducers for electric scan of the object.
There are various kinds of ultrasonic probes such as a one-dimensional-array probe, a two-dimensional-array probe, an annular-array probe, and so on according to arrangement of plural ultrasonic transducers, and ultrasonic probes of linear-scan type, sector-scan type, convex-scan type, radial-scan type, and so on according to scan type.
Among them, a two-dimensional array probe in which plural ultrasonic transducers are two-dimensionally arranged especially attracts attention. This is because, using the two-dimensional array probe, two-dimensional scan of the object is possible with an ultrasonic beam without moving the probe itself, and three-dimensional ultrasonic image information including information in the depth direction of the object (the traveling direction of ultrasonic waves) can be obtained. Thereby, an image representing a desired section of the object can be constructed and a stereoscopic image (3D image) of the object can be constructed (volume imaging can be performed).
If it is possible to generate a three-dimensional image by ultrasonic imaging, very useful diagnoses can be made in various medical fields. For example, in the obstetrics department, fetal diagnoses by observation of developing and growing of a fetus in real time in moving pictures can be performed. Specifically, early detection and treatment of fetal abnormality or the like may be possible by continuous observation of the volume change of a brain and growth of a spine. Alternatively, an attempt to provide treatment of a fetus within a body cavity is being made while referring to three-dimensional ultrasonic images. Further, in the cardiovascular department, a heart disease can be discovered by observation of volume change of a heart or the like based on three-dimensional ultrasonic images. Such demand is especially high in Europe and the United States. Furthermore, in the urologic field, there is so much interest in three-dimensional ultrasonic images.
However, there are much harder technical problems in fabrication of two-dimensional arrays than those for one-dimensional arrays. First, when ultrasonic transducers are arranged in a two-dimensional manner, the number of ultrasonic transducers dramatically increases. Accordingly, electrically leading out wires from the respective ultrasonic transducers becomes difficult. Secondly, since the number of shield wires drastically increases with the number of ultrasonic transducers, a cable for connecting the ultrasonic probe and an ultrasonic diagnostic apparatus main body becomes thick. Thereby, handling of the ultrasonic probe becomes difficult. Further, the large cable diameter is a critical defect in the ultrasonic probe for intracavitary observation.
As a related technology, Japanese Patent Application Publication JP-P2001-292496A discloses an electrode lead-out structure of a two-dimensional array probe. That is, in JP-P2001-292496A, the two-dimensional array probe is formed by connecting to one another a two-dimensional transducer, in which signal wires are passed through a backing material and signal electrodes as one ends of the signal wires are two-dimensionally arranged as an electrode pattern in parallel with the arrangement surface of vibrating elements, a relay substrate, on which the same electrode pattern as that of the signal electrodes, and an IC substrate to be coupled perpendicularly to the relay substrate.
However, according to the method of leading out wires, the connection of address electrodes may be uncertain. Therefore, it is extremely difficult to ensure the connection between 1000 to 4000 ultrasonic transducers, for example, and the electric wires, respectively.
Japanese Patent Application Publication JP-P2000-214144A discloses that, in an ultrasonic probe having vibrators arranged in a two-dimensional matrix form, an electric circuit connected to the respective vibrator elements for transmitting and receiving signals is configured of signal wires one-dimensionally arranged on a base film at intervals corresponding to that of the vibrator elements, and the two-dimensional arrangement ultrasonic probe is formed by sandwiching the base film part of the connection probe to the vibrator elements of the signal wires between acoustic absorbing materials to bond them. That is, in JP-P2000-214144A, the base films (flexible pattern circuits), on which plural signal wires are respectively formed, and the acoustic absorbing materials (backing materials) are alternately joined, and thereby, ends of the plural signal wires are two-dimensionally arranged in alignment with the arrangement of the vibrators in the two-dimensional matrix form.
However, in JP-P2000-214144A, connection uncertainty between the respective vibrators and the signal wires also remains. Further, according to the fabrication method of the ultrasonic probe disclosed in JP-P2000-214144A, since the ultrasonic transducers are arranged to form an ultrasonic radiation surface as a flat surface, it is possible to fabricate a flat array (sector scan array) to be used for chest observation, for example. However, it is impossible to fabricate a convex array having an ultrasonic radiation surface entirely with a convex surface (e.g., to be used for fetus observation).
Japanese Patent Application Publication JP-P2001-309493A discloses a two-dimensional array ultrasonic probe having a structure in which print substrates for leading out signal leads and ground wires from the respective vibrators at the respective column intervals of elements arranged in a matrix form is provided, and that a two-dimensional array transducer is formed by mounting a vibrator array for one column on the print substrate and then arranging the print substrates, on which the vibrators have been mounted, in the row direction.
Further, Japanese Patent Application Publication JP-P2005-210245A discloses that units, each including a print substrate, plural wiring lines formed with a predetermined pitch on the print substrate, plural multilayered piezoelectric elements arranged in one row such that the first sides of the elements contact with ends of the wiring lines respectively, a conducting thin plate that commonly connects the second sides opposite to the first sides of the plural multilayered piezoelectric elements arranged in one row, and a backing material formed to cover the wiring lines on the print substrate, are formed by being arranged side by side with a predetermined pitch. Further, the first sides and the second sides of the multilayered piezoelectric elements have conductivity, and, in the multilayered piezoelectric elements, plural piezoelectric materials and plural internal electrode layers are alternately stacked and the plural internal electrode layers are alternately connected to ones of the first sides or the second sides.
In JP-P2001-309493A and JP-P2005-210245A, a unit is fabricated by forming plural wiring lines side by side on a flexible print substrate, and connecting plural ultrasonic transducers to the wiring lines on side surfaces (surfaces perpendicular to the ultrasonic radiation surface) respectively. Then, a two-dimensional array is fabricated by stacking a plurality of the units. According to the fabrication method, the signal wire of each ultrasonic transducer can be reliably connected. However, it is also impossible to form the ultrasonic radiation surface of the two-dimensional array as a curved surface.